Engine arrangement for small planing watercraft

ABSTRACT

A small planing watercraft including a hull, a propulsion unit mounted on the hull and a high RPM-high output engine for driving the propulsion unit, wherein the engine includes at least one intake valve and an intake valve timing control system for advancing the opening and closing of the intake valve when the watercraft is operating below a predetermined speed corresponding to a velocity at which the watercraft transitions from non-planing to planing motion. The engine may also include a long air intake passage for low-speed operation and a short air intake passage for high-speed operation, with an air intake control valve in the short air intake passage that is closed when the watercraft is operating below the predetermined speed. The engine may also include an exhaust control valve for constricting the exhaust passage, and a system for at least partially closing the exhaust control valve when the watercraft is operating below the predetermined speed. The invention increases the lower RPM output of a high RPM-high output engine to enable faster transition of the watercraft between non-planing and planing operations. Engine intake air flows over the intake valve timing control to provide a cooling effect.

This application is a continuation of application Ser. No. 09/406,099filed on Sep. 27, 1999.

BRIEF SUMMARY OF THE INVENTION

The present invention addresses these and other drawbacks ofconventional technology by providing a small planing watercraft with ahigh-RPM, high-output engine which can make a smooth transition fromnon-planing to planing movement. The watercraft includes a hull orshell, a propulsion unit arranged in the hull, and an engine arranged inan engine compartment in the hull for directly driving the propulsionunit. The engine includes an exhaust passage, at least one air intakevalve, an air intake valve camshaft for opening and closing the airintake valve, and valve timing control means for advancing the normalclosure of the air intake valve when the watercraft and engine areoperating below a predetermined speed or RPM at which the watercrafttransitions from non-planing motion to planing motion. The predeterminedspeed of the watercraft is directly related to a predetermined engineRPM.

The valve timing control means may include a toothed intake camshaftdrive pulley mounted on the end of the intake valve camshaft andoperatively connected (e.g., by a toothed belt) with the crankshaft forrotation therewith, and means for selectively rotating the pulleyrelative to the intake camshaft for advancing the closure of the airintake valve when the engine is operating below the predetermined speed.More particularly, the selective rotating means may include an innershaft fixed on the end of the intake valve camshaft and having helicalsplines arranged on its outer surface. An annular sliding piston isslidably arranged around the inner shaft with helical splines on itsinner surface for engaging the splines on outer surface of the innershaft. The piston also has oppositely twisted helical splines on itsouter surface for engaging similar splines inside an interiorcylindrical opening of the pulley. All of the splines are arranged so asto rotate the pulley relative to the camshaft in response to axialtranslation of the annular piston.

The engine may also include a long air intake passage for low RPMoperation and a short air intake passage for high-RPM operation, with anair intake control valve provided in the short air intake passage thatincludes means for closing the air intake control valve when thewatercraft is operating below a predetermined speed. The engine mayinclude an exhaust passage having an exhaust control valve forselectively constricting the exhaust passage by partially closing theexhaust control valve when the watercraft is operating below thepredetermined speed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Various embodiments of the invention will now be described withreference to the following drawings wherein the same reference numeralsare used to refer to the same features in each of the figures.

FIG. 1 is a partial cutaway side elevational view of a small planingwatercraft including the present invention;

FIG. 2 is a sectional view taken long line II—II in FIG. 1;

FIG. 3 is a top plan partial sectional view of the cylinder head of theengine shown in FIGS. 1 and 2;

FIG. 4 is an enlarged section view of the valve timing controlapparatus;

FIG. 5 is a sectional view of a hydraulic pressure control apparatus foruse with the valve timing control apparatus;

FIG. 6 is a graph showing the relationship between valve position andcrank angle;

FIG. 7 is a graph showing the relationship between engine rpm, engineoutput, and water drag against the watercraft;

FIG. 8 is a partial sectional view of the engine compartment for anotherembodiment of the invention;

FIG. 9 is a transverse sectional view of the engine compartment of yetanother embodiment of the invention; and

FIG. 10 is a sectional view of an exhaust system of yet anotherembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present inventions will now be described withreference to FIGS. 1-7. FIG. 1 is a side view of a small planingwatercraft 1 which is operated by a rider (not shown) straddling a seat2 while grasping the handlebars 3 in front of the seat. The watercraft 1is supported by a hull or shell 6 including an upper deck 4, lower hull5, and a bulkhead 7 which separates the engine compartment 8 shown inthe cutaway portion of FIG. 1. The engine 9 is mounted in the enginecompartment 8 near the center of the for-and-aft length of the hull 6.Engine compartment 8 is defined at least in part by upper deck walls 4and the upper end of engine 9 extends between upper deck walls 4, asshown in FIG. 2.

A fuel tank 11 is mounted in front of the engine 9 and a crankshaft 10extends aft of the engine toward a conventional jet-type propulsionapparatus 12. Although each of the embodiments discussed below isdescribed with respect to a jet-type propulsion apparatus, an outboardengine or other suitable propulsion apparatus may also be used. Forwardand aft outside or fresh air intake ducts 13 and 14 having exit openings13 a, 14 a are arranged near the transverse center of the watercraft 1so as to draw air into the engine compartment 8 at locationslongitudinally spaced in front of and behind the engine 9. Thepropulsion apparatus 12 includes an impeller (not shown) which rotatesat the same speed as the crank shaft 10 in order to pump water throughthe jet outlet 12 a to propel the watercraft. The jet outlet 12 a isthen rotated by the moving the handlebars 3 to steer the watercraft.

The engine 9 illustrated in the Figures is a water-cooled,twin-cylinder, DOHC-type internal combustion engine. As shown in FIG. 3,it has two intake valves for each cylinder that are operated by anintake valve camshaft 15, and two exhaust valves for each cylinder (notshown) that are operated by an exhaust valve camshaft 16. Each of thecamshafts 15 and 16 are installed in the cylinder head 17. The intakevalve camshaft 15 is mounted on the port, or left, side of the engine 9with one end connected to the charge (air and fuel) intake system 18while the exhaust camshaft 16 is mounted to the starboard, or right,side and is connected to an exhaust manifold 19.

As shown in FIG. 2, the intake system 18 includes a carburetor 21connected by an intake duct 20 to the cylinder head 17. An air intakesilencer 22 is arranged upstream of the carburetor 21 on the port sideof the watercraft 1 and includes an air intake opening 23 which drawsair from inside the engine compartment 8. Air that enters the forwardair intake duct 13 exits the opening 13 a flows upwardly past, andcools, the valve timing control apparatus 31 (discussed below) beforeentering the air intake opening 23 in the silencer. Similarly, air thatenters the aft intake duct 14 flows exits opening 14 a and flowsupwardly and cools the hydraulic pressure control apparatus 34 (alsodiscussed below) enroute to the engine air opening 23.

The exhaust manifold 19 is connected through an exhaust pipe 24 thatleads from the cylinder head 17 to the water lock 25 shown in FIG. 1.The water lock 25 expels the exhaust gases into the pump chamber of thepropulsion apparatus 12 and then out through the exhaust gas outlet 19a. When the hull 6 is operating in a non-planing state, the water jetoutlet 12 a is submerged so that the exhaust gases are expelledunderneath the surface of the water. When the hull 6 is operating in aplaning state, the water jet outlet 12 a is positioned above the surfaceof the water so that the exhaust gases are expelled into the atmosphere.

As shown in FIGS. 1-3, a toothed belt drive apparatus 26 is arranged onthe front side of the engine 9 that is connected to and transmits therotation of the crank shaft 10 to the intake valve camshaft 15 and theexhaust valve camshaft 16. Each of the crank shaft 10, camshaft 15 andcamshaft 16 includes a respective toothed pulley 27, 28, and 29, whichare engaged and are driven by a toothed belt 30.

As best shown in FIG. 3, a valve timing control apparatus 31 is mountedon the front side of the intake valve camshaft 15, while aflywheel/magneto 32 is mounted on the front side of the crankshaft 10.As described in more detail below, the valve timing control apparatus 31uses hydraulic pressure to adjust the timing phase of the intake valvecamshaft 15 relative to the exhaust camshaft 16, and hence the openingand closing interval of the intake valves relative to the crankshaftrotational angle.

As shown in FIG. 3, the valve timing control apparatus 31 includes acontrol or actuating unit 33 arranged on the front end of the intakevalve camshaft 15 and a hydraulic pressure control apparatus 34 arrangedat the rear end of the intake valve camshaft. As shown in FIG. 4, thecontrol unit 33 includes a bolt 35 which secures an inner shaft 36 tothe end of the intake valve camshaft 15. An annular sliding actuatingpiston 37 slidably fits over the outside of the inner shaft 36 andinside an outer cylinder 38 of the intake valve camshaft pulley 27 whichpreferably is integrally formed as one piece with the pulley. An oilsupply passage 39 is bored through the center of the attachment bolt 35and on one end communicates with a second oil passage 40 and an enginelubricating oil pressure supply passage 47 formed in the intake valvecamshaft 15 as shown in FIG. 3. The opposite end of the oil passage 39communicates with an oil pressure receiving chamber 41 on the front sideof the cylinder 38 so that hydraulic pressure received in the oilpressure receiving chamber 41 will be applied against the face of thesliding piston 37 opposite the camshaft 15.

The actuating piston 37 includes a primary piston 37 a and a secondarypiston 37 b which are joined by bolts 37 c and a small compressionspring 37 d. A larger compression coil spring 42 normally urges thesliding piston 37 away from the camshaft 15. Helical splines 43 and 44twisting in opposite directions are arranged on the inner and outercircumferential surfaces of the sliding piston 37 and mate withcorresponding adjacent helical splines 45 and 46 on the outercircumference of the inner shaft 36 and the inner circumference of thecylinder 38, respectively. The helical splines cause the intake valvecamshaft 15 to rotate in an advance direction relative to the pulley 27when the piston 37 is translated in the aft direction. Thus, increasedhydraulic pressure in the oil chamber 41 urges the sliding piston 37 tothe right in FIG. 4, or aft in the watercraft 1, so as to cause theintake valve camshaft 15 to rotate forward in the same direction as itis rotating through a predetermined angle with respect to the pulley 27.

FIG. 5 illustrates the structure of the pressure control apparatus 34that selectively drives and releases the sliding piston 37 by openingand closing the engine oil passage 40 inside the intake valve camshaft15. The pressure control apparatus 34 includes a control valve 48 withina housing 50 which is secured to the aft end of the camshaft 15, and aplunger 52 that slides freely inside the housing against a compressionspring 51. FIG. 5 illustrates the plunger 52 in the normal pressurerelease position at which oil holes 50 a and 52 a are in communicationso as to allow oil to flow out of the oil passage 40 in whichpressurized engine lubricating oil is circulated.

The plunger 52 is selectively driven by a solenoid 49 including ahousing 49 a in which a coil 49 b into which an armature rod 49 c isinserted are located. A controller (not shown) senses engine speed (RPM)from the crankshaft 10, camshaft 15 or camshaft 16 and switches thesolenoid from an OFF state to an ON state by applying a current to thecoil 49 b while the engine speed is below a certain level. This, inturn, causes the rod 49 c to move toward the left in FIG. 5, restrictingor stopping the flow of oil between oil holes 50 a and 52 a and therebypermitting the pressure in passages 39, 40 to be at a high level, andlikewise in oil chamber 41. The increased pressure in the oil pressurereceiving chamber 41 urges the sliding piston 37 toward the right inFIG. 4 against the force of the coil spring 42.

As the piston 37 moves aft in the watercraft 1, the helical splines43-46 cause the intake valve camshaft 15 to rotate in a forwarddirection over a predetermined angle with respect to the pulley 27which, in turn, advances the timing phase of intake camshaft 15 relativeto the exhaust camshaft 16. As discussed in more detail below, thistiming change causes the air intake valves to close earlier and to openearlier relative to (overlap longer with) the exhaust valves. Incontrast, when the solenoid 49 is in the OFF state at high engine speedabove a predetermined RPM, the plunger 52 slides to the right in FIG. 5so that the engine lubricating oil inside the passage 40 flows throughthe oil holes 50 a and 52 a and into the valve chamber of the cylinderhead 17. The ensuing release of pressure in oil chamber 41 allows theintake camshaft 15 to return to its original position by means of spring42.

In the embodiment discussed above, the engine 9 uses lift-type valvesfor the intake and exhaust valves, and a valve timing which is asuitable for high-RPM, high-output engines. FIG. 6 illustrates thepositions of these valves versus crank angle with the exhaust valvepositions shown in the left curve (left of the top dead center crankposition) and the intake valve position shown in the two curves on theright (following the top dead center position). During high-speedplaning motion of the watercraft at high engine RPM as depicted by thesolid-line curves in FIG. 6, the exhaust and intake valves operate withminimal overlap at the top dead center crank position. However, when theengine 9 is operated at lower RPM (during low- to mid-speed, non-planingmotion) the valve timing control apparatus 31 causes earlier closure ofthe intake valves and lengthens the overlap period as shown by thebroken-line intake valve curve in FIG. 6. This provides greater outputof the engine at lower RPM's.

FIG. 7 illustrates engine output (in the broken-lines) and drag (in thesolid-line) verses engine RPM (and watercraft velocity), for a typicalwatercraft 1. The solid-line drag curve illustrates how below speed A,the watercraft 1 operates in a non-planing mode where the bow of thewatercraft 1 parts the water as it advances, similar to cruising modefor a water displacement craft. As its speed increases to speed B, thewatercraft hull 6 begins planing over the surface of the water. Duringthe transition from non-planing motion below speed A, to planing motionat and above speed B, the bow of the watercraft 1 gradually rises out ofthe water and drag increases until a hump is crossed between A and B. Ifthe engine power output during the transition from non-planing toplaning motion is insufficient, then the watercraft will be unable tomove through the transition zone and into the planing mode at speed B orwill transition too slowly.

As illustrated by the broken lines in FIG. 7, engine output generallyincreases with increasing engine RPM. However, as depicted by theevenly-spaced broken lines in FIG. 7, low-speed engines typicallyprovide higher torque and power output at lower engine RPM thanhigh-speeds high output engines. Conversely, high-speed enginesgenerally provide higher output at higher engine RPM, as depicted by theunevenly-spaced broken lines in FIG. 7. Consequently, for engine RPMsbelow speed C, it is preferable to have an engine with low-speed engineoutput characteristics, while at speeds above speed C, it is preferableto have an engine with high-speed output characteristics.

Low-speed engine output characteristics can be obtained neverthelessfrom the high-RPM, high-output engine 9 by using the valve timingcontrol apparatus 31 to advance the opening and closing time of theintake valves. Thus, engine speed C, where the low- and high-speedoutput engine lines cross, is the desired preselected RPM level at whichthe controller discussed above switches the solenoid 49 ON in order toenhance the low speed output of the engine. The solenoid 49 can also beswitched ON at RPM level B when the watercraft 1 is moving through thetransition zone from non-planing to planing motion. Thus, the high RPMhigh output engine 9 can be selectively controlled so as to producesufficient output at lower engine speeds to move smoothly “over thehump” as the watercraft makes the transition from non-planing to planingoperation.

Output of an engine of the type discussed is enhanced during low-andmid-speed operation by advancing the timing of the intake valves forseveral reasons. First, the timing change eliminates the blow-back ofintake air into the combustion chamber following the intake stroke.Second, the longer exhaust valve overlap interval increases the exhaustpressure and internal exhaust gas recirculation (“EGR”) so as to reducepumping losses when the pistons descend on the intake stroke. Thislatter effect is particularly important during non-planing operationswhen the exhaust outlet 19 a is submerged underwater so as to increasethe exhaust back pressure. The control apparatus 31 can also be set toexclude operation during certain periods, such as start-up or idling, inorder to shorten the intake and exhaust valve overlap interval andimprove engine performance during those periods.

FIG. 8 illustrates another embodiment of the invention related to anengine compartment 8 of a small planing watercraft 1. In thisembodiment, the valve timing control apparatus 31 is arranged on theintake valve camshaft 15 near the aft, or rear, side of the engine 9relative to intake opening 23. Consequently, when the engine is running,air enters the engine compartment 8 from the exit 14 a of the rear aftair intake duct 14 and cools the timing control apparatus 31 and controlunit 33 as it is drawn towards and into the air intake opening 23 of theair intake silencer 22 (not shown and FIG. 8). FIG. 8, incidently, alsoillustrates a bilge pump apparatus 61 for removing water that collectsat the bottom of the hull of the watercraft 1.

FIG. 9 is a transverse sectional view of the engine compartment foranother embodiment of a small planing watercraft 1. In this embodimentthe engine block 9 is tilted laterally about its longitudinal axis sothe cylinder head 17 is located towards one side of the engine fly wheel32 and, the cylinder head 17 of the engine 9 is connected to the airintake silencer 22 by an intake manifold 61 which has a relatively shortintake passage 62 for high-speed operations, and a relatively longintake passage 63 for low speed operations. In particular, the intakemanifold 61 includes a substantially straight intake passage 62 forhigh-speed operations, and a longer S-shaped, or otherwise curved intakepassage 63 for low-speed operations. Each of the intake passages 62 and63 is connected at the engine at an area 65 where a fuel injector 64sprays fuel into the intake air. As seen in FIG. 9, the tilted engineconfiguration provides ample space for the intake passages 62 and 63 onthat side of the engine located further away from the wall of upper deck4 without requiring enlargement of the engine compartment to accommodatethe intake passages.

A throttle valve 66 is arranged in the low-speed intake passage 63,upstream from the connecting area 65. A similar throttle valve (notshown) is arranged in the high-speed intake passage 61 along with an airintake control valve 67 installed upstream of the throttle valve. Thethrottle valves 66 are opened and closed by a linkage to the throttlegrip mounted on the handlebars 3 as shown in FIG. 1. The air intakecontrol valve 67 is operated by an air intake valve controller (notshown) which senses the engine RPM from the crankshaft 10, camshaft 15,camshaft 16, or the engine ignition system. When the engine RPM is lowerthan that shown at C in FIG. 7, the air intake controller closes the airintake control valve 67. Conversely, the air intake control valve 67 isopened when the engine RPM is higher than speed C, indicating that thewatercraft 1 is planing. During high-speed planing motion above speed C,the engine 9 will draw large volumes of air through the straight airintake passage 62. When the engine speed falls below the planingtransition speed B, engine output is improved by taking advantage of thewell known air intake inertia effect available in the longer air intakepassage 63 and directing intake air through the longer passage.

FIG. 10 illustrates an embodiment of an exhaust system for a smallplaning watercraft 1 including a water-cooled, four-cycle,three-cylinder engine 71 having a cylinder head 72 fitted with cylinderbores 74 and spark plugs 75. In FIG. 10, the port side of the cylinderhead 72 is attached to the exhaust manifold 73 while the air intakesystem is arranged on the starboard side of the cylinder head. Theexhaust manifold 73 merges the exhaust passages from each of the threecylinders 74 and leads to an exhaust pipe 76. The exhaust pipe 76 thenextends along the starboard side of the watercraft 1 to the water lock25 shown in FIG. 1. A coolant passage W is formed by a double-walledstructure of the exhaust manifold 73 and extends from the coolant outlet71 to area G midway down the exhaust pipe 76. After cooling the exhaustmanifold 73 and exhaust pipe 76, the water in the coolant passage W isexpelled into the area G, or through a water drain hose 77 leadingoutside the hull of the watercraft.

A catalyst 78 and exhaust control valve 79 are installed in thedouble-walled area of the exhaust pipe 76. Multiple exhaust controlvalves 79 may also be installed in the exhaust manifold 73 for each ofthe cylinders, as shown by the double-dashed lines in FIG. 10. Theexhaust control valve(s) 79 is/are linked by a drive mechanism,including a pulley 79 a and a cable 79 b, to an exhaust valve controller(not shown). When the exhaust control valve 79 is partially closed,pressure waves propagating through the exhaust passage G are reflectedoff of the valve and back into the combustion chamber during the valveoverlap interval. The exhaust valve controller partially closes theexhaust control valve 79 when the engine speed is less than speed C inFIG. 7, and opens the control valve 79 when the speed is higher thanspeed C. Consequently, when the watercraft is making the transition fromnon-planing to planing motion between speeds B and C, the exhaust valve76 is closed, except for a small gap, until the engine reaches speed Cwhen the valve is opened, or partially opened.

In this embodiment, when the engine rpm is high enough that thewatercraft 1 begins planing, the exhaust control valve 79 is opened soas to lower the exhaust back pressure and obtain full high RPM poweroutput. Conversely, when the engine speed is low and the watercraft 1 isoperating in a non-planing or transition condition, the exhaust passageG is restricted so as to reflect the exhaust pressure waves and boostlow RPM engine power as the watercraft 1 moves through the transitionzone.

The invention described above offers numerous advantages overconventional small planing watercraft technology. For example, advancingthe closure of the intake valves increases engine output at low speed byeliminating blow-back at the end of the air intake stroke. Similarly,lengthening the overlap interval between the intake and exhaust valvesincreases the exhaust pressure and decreases the pumping loss duringintake piston descent. Using an intake system with separate air intakepassages for low- and high-speed operations takes advantage of theinertial effect of air moving through the longer passage to boost engineoutput under low speed conditions. Constriction of the exhaust passageby one or more exhaust control valves utilizes exhaust gas pressurewaves in order to boost engine output at low speeds. Consequently, thehigh-speed, high output engine 9 has more power at lower RPM to move thewatercraft smoothly and quickly over the hump in making the transitionfrom non-planing to planing motion. Furthermore, by arranging the valvetiming control apparatus between the opening of the main air intake ductof the hull and the engine air intake opening, the flow of air insidethe engine compartment cools the valve timing control apparatus andimproves its life. Likewise, the oil pressure control 34 is cooled byair moving over the control from aft air duct 14.

While the technology discussed above has been discussed with respect tovarious preferred embodiments and configurations, this description ismerely illustrative of some of the many useful forms in which theinvention might be reduced to practice by one of ordinary skill in theart. The scope of the protection for the invention is defined by thesubject matter of the following claims when they are properly construedand interpreted in light of the description provided above.

What is claimed is:
 1. A small planing watercraft having a piston-typeinternal combustion engine, said engine comprising a high speed-highoutput engine normally developing maximum power output at a relativelyhigh RPM, said engine including an air intake opening and a rotatableintake valve camshaft actuating at least one intake valve of the engine,wherein said camshaft is driven in synchronous rotation by a camshaftdriving device drivingly connected to a crankshaft of the engine andcoupled to one end of the camshaft and further wherein said intake valvehas normal opening and closing time intervals relative to engine pistonand crankshaft positions, said normal opening and closing time intervalsarranged to effect said high RPM-high output operating characteristicsof said engine, the improvement comprising: a variable intake valvetiming device connecting the camshaft driving device to the camshaft andincluding an intake valve timing control device located adjacent to oneend of the engine longitudinally spaced from said intake opening whereinintake air is caused to flow over the valve timing device en route tothe engine air intake opening during engine operation; said intake valvetiming control device arranged so that during engine operation below apredetermined engine speed at which the engine develops less thanmaximum power output, the relative driving position of the camshaftdriving device and the camshaft is selectively adjusted to advance thetiming of the intake valve opening and closing relative to the camshaftdriving device, and the relative driving position of the camshaftdriving device and the camshaft is adjusted to restore the normaldriving relationship between the camshaft driving device and thecamshaft when the engine is operated at speeds above said predeterminedspeed; whereby said engine may produce higher power output at operatingspeeds below said predetermined speed as compared with engine operatingcharacteristics without advancement of intake valve opening and closing;and an outside air intake duct having an exit opening spaced away fromsaid intake valve control device on a side thereof opposite the sidetoward which the engine intake opening is located, whereby intake air iscaused to flow over the intake valve control device enroute to theengine air intake opening during engine operation.
 2. The improvement asclaimed in claimed in claim 1, wherein said camshaft driving deviceincludes a toothed element drivingly connected to said one end of theengine intake valve camshaft and said variable intake valve timingsystem is actuatable via said control device to selectively rotate thetoothed element relative to the camshaft.
 3. The improvement as claimedin claim 2, wherein said annular toothed element includes internallongitudinal helical splines extending along an inner cylindricalcircumferential surface of the element; and wherein said variable intakevalve device includes an inner shaft fixed to and extendingconcentrically with said one end of said intake valve camshaft; saidinner shaft including outer helical splines extending axially over aperipheral surface thereof; said inner splines of said toothed elementand said outer splines on said inner shaft twisting relative to eachother; an annual sliding member located between said inner shaft andsaid inner cylindrical circumferential surface of said toothed element,said sliding member having axial splines on inner and outer peripheralsurfaces thereof that are engaged with said splines of said inner shaftand said inner cylindrical circumferential surface of said toothedelement; and a sliding member driving system operatively connected tothe sliding member in a manner so that, upon actuation of the drivingsystem, the sliding member is axially driven relative to the inner shaftand toothed element to thereby cause relative rotation between thetoothed element and the camshaft.
 4. The improvement as claimed in claim3, wherein said annular member is a piston slidably mounted in saidinner cylindrical surface of said toothed element and said slidingmember driving system comprises a hydraulic circuit including apressurized engine lubricating oil delivery conduit arranged toselectively deliver pressurized engine lubricating oil to at least oneside of said piston to thereby cause its displacement relative to saidcylindrical surface in a direction that advances the position of thecamshaft relative to the toothed element; said intake valve timingcontrol device comprising a hydraulic pressure control device arrangedto selectively supply pressurized engine lubricating oil to said atleast one side of said piston and to selectively drain said pressurizedhydraulic fluid away from said at least one side of said piston.
 5. Theimprovement as claimed in claim 4, including a spring arranged to biassaid piston towards a position at which the relative position of saidtoothed element and camshaft cause said normal opening and closing timeintervals of said at least one intake valve.
 6. The improvement asclaimed in claim 4, wherein said engine lubricating oil delivery conduitextends longitudinally through said camshaft to an end thereof oppositethe end to which the toothed element is affixed; and including ahydraulic pressure regulator located at said end of the camshaftopposite the end to which the toothed element is affixed, said pressureregulator arranged so that oil pressure is selectively controlled insaid fluid delivery conduit in response to engine operating speed. 7.The improvement as claimed in claim 6, wherein said conduit in saidcamshaft contains lubricating oil circulating through and out of saidconduit when said engine is operating, and an actuator for saidhydraulic pressure regulator is arranged so that upon its actuation,circulation of said lubricating oil out of the conduit is blocked toincrease the pressure of the oil in said conduit; said actuator arrangedso that it is selectively electrically activated in response to engineoperating speed above said predetermined speed.
 8. The improvement asclaimed in claim 3, wherein said inner splines of said toothed elementand said helical splines of said inner shaft twist helically in oppositedirections.